Headlight photometer



Dec; 17, 1929. c s, RlcKER 1,739,650

HEADLIGHT PHOTOMETER Filed Jan. 23, 1928 y A 7 I l V 7 z l "0: 'y I gvmmwtow fiis 7259 5. 2/ 6765/6;

(1H0: up

Patented Dec. 17, 1929 UNITED STATES CHESTER S. RICKEB, OF WAUKESHA, WISCONSIN HEADLIGHT PHOTOMETER Application filed January 23, 1928. Serial No. 248,859.

It is the object of my invention to produce a device which may be employed in determining whether or not the headlights of an automobile conform with legal requirements relative to the intensity of illumination at various points in the projected beam. More specifically, it is my object to provide such a device in which the expense and trouble involved in maintaining a plurality of stand 2rd lamps may; be eliminated. A further object of my invention is to produce a headlight photometer 'which can be utilized in testing the characteristics of beams projected from automobile headlights located at different heights. In accomplishing the above objects I provide a means for comparing the intensity of illumination at predetermined points in the headlight beam with the intensity of illumination derived from an independent standard light-source, and I provide a frame or support in which the independent lightsource and the light-comparing means may be mounted in any one of a series of predetermined positions in the headlight beam.

The accompanying drawing illustrates my invention: Fig. 1 is a rear elevation of a complete photometer; Fig. 2 is a vertical section on the line 22 of Fig. 1; Figs. 3 and 4 are respectively vertical and horizontal sections through the enclosure containing the independent light-source and the means for comparing the illumination derived therefrom with the intensity of the illumination at various points in the projected beam from the headlights.

The support for the independent'lightsource and its enclosure is preferably in the form of a screen 10 so mounted that it may be vertically adjusted. In the drawings, I have shown the frame 10 as supported from two spaced hollow standards 11 each provided with a pulley 12 over which there passes a cable 13 secured at one end to the screen 10 and at the other to a counterweight 14 located Within the hollow standard. In the screen precise construction of the support for the screen 10 is no part of my invention, and it may be modified in any desired manner.

The wording of laws describing the characteristicsof the beam projected by the headlights of an automobile varies considerably, but such laws usually specify that at a certain distance, generally 100 feet, from the headlights the intensity of illumination at various points shall have maximum and minimum values. As a rule, the points at which a minimum intensity of illumination is required are located in the lower part of the beam, while those at which a maximum intensity is permitted are located in the upper part of the beam. The locations of the points at which permissible intensity of illumination is prescribed are usually determined by specifying their distance from the right or left of the projected center line of the automobile and their heights relative either to the roadway or to the height of the headlight. In practice, I have found it inconvenient to measure the intensity of illumination at a distance as great as 100 feet in front of the headlights to be tested, and I therefore contemplate locating my photometer at some lesser distance from the headlights. This necessitates a corresponding reduction in the horizontal and vertical distances between the various openings 16, and I am therefore enabled to employ a much smaller screen 10 than would be required if I located my photometer at a greater distance from the headlights. headlights also necessitates an alteration in 'the height of the photometer as a whole.

This alteration is not a constant one, because of the fact that there is considerable variation in the heights at which headlights are mounted on automobiles of various makes. It is for this reason that I make the photometer screen 10 adjustable in height, as I am thus enabled to locate it vertically in the proper position to determine the characteristics of the beam projected from the headlights being tested.

The arrangement of the independent lightsource and the character of the light-comparing means may be modified as desired, but-I prefer to employ an independent light-source Moving the photometer nearer the in the form of an electric lamp bulb 20 having a predetermined lumen output. The intensity of illumination from the lamp 20 may be compared with that of the headlight beam by means of two juxtaposed blocks 21 and 22 of translucent material, the former receiving. light from the lamp and the latter from the headlights being tested. The two blocks are preferably separated by a thin opaque screen 21*. Desirably, I provide for the lamp bulb 20 and the light-comparing means an enclosure in the form of a box 23 having in one side an opening 24 adapted to be brought into alinement with any of the screen openings 16. A reflecting prism 25 serves to direct light received through the opening 24 to the block 22. An opening 26 located in the wall of the enclosure 23 in line with the junction of the blocks 21 and 22 0 permits the intensity of the illumination received vfrom the lamp 20 to be compared with that from the headlights being tested. As the required intensity at the various openings 16 differs, I provide means by which 25 the lamp 20 may be set at various measured distances from the block 21. To this end, I may attach to the base 28 which supports the lamp 20 a rod 29 which extends through one end of the box 23 and is provided with a 30 series of graduations by means of which may be determined the intensity of the illumination received by the block 21 from the lamp bulb 20. a

In order to make certain that the lamp bulb 5 20 emits light of the correct intensity, it may be supplied with current from a battery or other suitable current source, the lamp circuit including an ammeter 36 and a variable resistance 37. By operating the variable re- 7 40 sistance the current strength. can be regu lated to control the intensity of illumination from the lamp 20. 1 1

On the rear face of the screen 10 I provide a plurality of sets of brackets 31 by means of which the box 23may be supported with the light-receiving opening 24 in line with any of the openings 16 in thescreen 10.

Two methods may be employed for determining whether or not the intensity of illumi- 60 nation at any of the openings 16 complies with the law. One method is to set the lamp 20 at such a position in the box 23 that the intensity ofthe illumination received by the block 21 will correspond with-that legally specified for the point in the headlight beam at which the intensity thereof is being tested. By observing through the opening 26' the relative brightness of the blocks 21 and 22, the operator can determine-whether or not the intensity of the light received through the opening 24 is above or below the specified -value. If the window 16 is located at a point where a minimum intensity of illumination is required, the beam complies with the law if the block 22 is as bright or brighter than the block 21. If, on the other hand, the window 16 is located at a point where a maximum 1I1- tensity is specified, the block 22 should not appear brighter than the block 21 but may,

appear less bright. p

By the other method of operating, the box 23 is supported by the brackets-31 with the light-receiving opening 24 in line with one of the screen openings 16, and the rod 29 is ad-,

justed to vary the position of the lamp bulb 20 until the blocks 21 and 22 appear of equal brightness, which indicates that the intensity of illumination received from the lamp bulb 20 by the block 21 is equal to that received' by the block 22 from the headlight. By reading the graduations on the rod 29, the operator can determine the intensity of illuminationreceived by the block 21; and by comparing that with the legal requirement at thepoint in, the beam corresponding to the position of the light-receiving opening 24 he is enabled to determine Whether or not the intensity of the beam at that point complies with the law.

The screen 10 plays no part in measuring the intensity of illumination at various points I in the headlight beam, and it may therefore be dispensed with. I find it desirable, however, to provide the screen'lO, forthe pattern oftthe projected headlight beam is admirably indicated thereon; and advantage may be of current consumed. Further, I eliminate the trouble involved in maintaining a plurality of lamp bulbs at a predetermined lumen output. v

I claim as my invention I 1.A headlight photometer, comprising a screen having a vplurality'of apertures arranged to receive light at predetermined angles from a headlight at a predetermined distance from the screen, an enclosure, a lightsource within said enclosure, said enclosure being provided with an openlng adapted to receive light from an exterior source, and means for comparing the intensity of lllumination received through said opening with that of said light-source, said enclosure being movable'relatively to said screen so that the opening in the enclosure may be brought into alinement with any of the apertures in said screen to' receive light from said headlight.

2. A headlight photometer as set forth in claim 1 with the addition of screen-supporting'means, and means for vertically adjusting said screen relatively to said screen-sup porting means. 1

3. A headlight photometer, comprising ascreen having a plurality of apertures arranged to receive light at predetermined angles from a headlight at a predetermined distance' from the screen, an enclosure, a lightsource within said enclosure, said enclosure bein provided with an opening adapted to receive light from an exterior source, means for comparing the intensity of illumination received through said opening with that of said light-source, said enclosure being movable relatively to saidscreen so that the opening in the enclosure may be brought into alinement with any of the apertures in said screen to receive light from said headlight,

andmeans in the vicinity of each screen aperture for supporting said enclosure in pos1- tion with its opening alined with such aperture.

4. A headlight photometer, comprising an enclosure having an opening adapted to receive light whose intensity is to be measured,-

means Within said enclosure for measuring the intensity of light received through said opening, and a support for said enclosure having means for locating said enclosure in any one of a plurality of positions on said support in order that the opening in said enclosure may receive light at predetermined angles from a headlight at a predetermined distance from said support.

' -5. A headlight photometer as set forth in claim 4 with the addition of means for vertically adjusting said support.

. In witness whereof, I have hereunto set my hand at Indianapolis, Indiana, this 20th day of January, A. D. one thousand nine hundred and twenty-eight.

' CHESTER S. RICKE-R. v 

